docs: update docs

docs/src/SUMMARY.md

@@ -18,6 +18,7 @@
 # for Admins
 
 - [Install with Docker](./admins/install-with-docker.md)
+- [Create Account](./admins/create-account.md)
 
 # for Developers
 

docs/src/admins/create-account.md

@@ -0,0 +1,27 @@
+# Create Account
+
+Ensure you set `HATSU_ACCESS_TOKEN` correctly in the [previous section](./install-with-docker.md) first, otherwise you will not be able to use the Hatsu Admin API.
+
+## just
+
+The easiest way to create an account is the [`just`](https://github.com/casey/just) command line tool:
+
+```bash
+just account create example.com
+```
+
+If you are using docker, you need to exec to the container first.
+
+```bash
+docker exec -it hatsu /bin/bash
+```
+
+## curl
+
+You can also access the API via curl, as `Justfile` does.
+
+```bash
+curl -X POST "http://localhost:$(echo $HATSU_LISTEN_PORT)/api/v0/admin/create-account?token=$(echo $HATSU_ACCESS_TOKEN)" \
+  -H "Content-Type: application/json" \
+  -d "{\"name\": \"example.com\"}"
+```